String folding should respect newlines and configured line length limit

[petteyg]

Would be nice if string concatentation folding respected newlines, i.e.

"abc\n" + 
"def"

or

"abc" + 
"\ndef"

would not get folded into one line.

Would also like to see it respect "Right margin" in Code Style settings. I have some SQL statements defined in concatenated literals in my code that get folded into 10,000 characters of horizontal scrollbar.

[cheptsov]

Yes, I'd like to fix this soon.